Explored the effect of non-signal and signal stimuli conditions upon skin conductance (SC) and finger pulse amplitude (FPA) of 8 schizophrenic patients and 6 normal controls. Both groups were assessed on a reaction time (RT) task that consisted of visual, auditory and tactile stimuli. Schizophrenics were significantly slower in the perception and reaction to visual, auditory and tactile stimuli than the normal volunteers. The autonomic reactivity of schizophrenics and normals was nonsignificant during the relaxation and non-signal stimuli conditions. However, when schizophrenics were asked to respond to signal stimuli or when an interfering stimulus was introduced, an autonomic imbalance was observed. The concept of directional fractionation provides the theoretical framework for the discussion of the autonomic results.